This invention relates to a mechanism for feeding sheetlike workpieces into a press one after another in timed relation to the up-and-down motion of an upper die or of a press slide for carrying the upper die.
A press infeed mechanism has been known which comprises a pair of gripping jaw assemblies mounted to a carriage movable toward and away from the press dies in step with the up-and-down motion of the upper die. The gripping jaw assemblies grip one workpiece in the retracted position of the carriage, carry the workpiece into the press with the carriage, and release and deposit the workpiece on the lower die. A problem has been encountered in returning the gripping jaw assemblies to the initial position. In order for the jaw assemblies not to interfere with the next workpiece to be fed into the press, the carriage with the jaw assemblies has heretofore been first moved upwardly from the loading position, then backwardly, and then down to the initial retracted position. Such back-and-forth and up-and-down movements of the carriage with the jaw assemblies necessitate, of course, very complex and bulky means, materially adding to the manufacturing cost of the press system including the infeed mechanism.
The known press infeed mechanism has had another problem arising in changing die assemblies, as the operation of the infeed mechanism is timed to the up-and-down motion of the press slide. The usual die-changing practice in presses of the type under consideration is to mount a new die assembly on a bolster plate and, after removal of the old die assembly with its bolster plate from the press, to introduce the new die assembly into the press for deposition on its bed via the bolster plate. Then the slide is lowered onto the upper die, and the latter is clamped onto the former. As the slide is subsequently raised with the upper die, the press is ready to resume operation with the new die assembly.
However, since the carriage travels forwardly with the descent of the slide, the pair of gripping jaw assemblies carried thereby would collide with the die assembly on the bolster plate unless measures were taken against such collision. One conventional measure has been to make the jaw assemblies retractable in the loading position of the carriage, thus unnecessarily making the infeed mechanism complex in construction. It has also been known to remove the jaw assemblies from the carriage, but this adds to the labor involved in die change.